Compressed air is used in various fields of industry including machinery, electronics, medicine, foods, and the like. However, since condensate, particles, and oils can cause problems such as degraded performance, adhesion, and damage in pneumatic devices that utilize compressed air, it is vital that a moisture remover, oil remover, and particle remover also be used.
Here, a pneumatic device can be defined as a device that converts the mechanical energy of a compressor or blower into pneumatic energy, adequately controls this compressed air using a control valve, etc., and supplies it to an actuator, to thereby provide the output in the form of mechanical energy suited to the load demand. Generally, the compressed air is provided by compressing the air of the atmosphere, but since atmospheric air includes various contaminants such as moisture, dust, etc., mixed therein, the process of compressing the air with a compressor may entail the contaminants being compressed together, resulting in an increased level of contamination.
In addition to substances entering together with the air inflow, substances such as lubricant oil, sealant, residue from filter elements, metal particles ground off from friction, and rust particles from corrosion may enter during the process of compressing the air. As such, a device for cleansing the compressed air is needed.
A compressed air purification apparatus for according to the related art, which may be called an “air filter” if it is a regular type and may be called a “mist separator” or a “demister” if it is specialized to removing water, may use a filter element that includes a porous part having minute pores for removing the moisture contained in the compressed air. The principle adopted here is that when the compressed air passes through the filter element, the moisture may be filtered and collected at the minute pores.
Since the conventional filter element is composed of a porous part, made from materials such as fabric, plastic, metal, etc., a “blockage” phenomenon inevitably occurs with the passage of time, due to sediments or microorganisms. Thus, while a filter element may function normally for a certain period of time after it is newly installed, the minute pores may eventually be blocked as time passes. As the blockage progresses, the cross-sectional area available for the air to pass through may decrease, and it may become increasingly difficult for the compressed air to pass through. This would result in increased pressure loss, which in turn would result not only in wasted energy but also in the pressure at the output end being lower that the required pressure. Hence, if the pressure difference between the front end and rear end of the filter element exceeds a certain level, it may be necessary to replace the filter element.
In other words, the filter element is an expendable part that must be replaced regularly, but if the filter housing is not transparent, the filter element may not be visible and determining the degree of blockage may be difficult, so that the appropriate time for replacing the filter element may be overlooked. Moreover, the higher the level of purity required of the compressed air, the smaller the pores must be in the filter element used, whereby the occurrence of such blockage is more significant in filter elements having more finely minute pores. Also, in order to discern the correct time for replacing the filter element, pressure gauges may be installed respectively on the front end and rear end of the compressed air dehumidifier, or a differential pressure gauge may be installed to check the pressure difference, but this would entail increases in equipment costs, installation space, and maintenance costs.
To address these drawbacks of the filter element, a purification apparatus utilizing centrifugation (cyclones) has been proposed.
A centrifuge-type apparatus for purifying compressed air according to the related art can be found in the Patent Document (Korean Patent Application Publication No. 10-2008-0078791).
The centrifuge-type compressed air purification apparatus according the related art may include an exhaust drum installed within the housing and spiral grooves formed in the circumference of the exhaust drum, where contaminants are made to gather at the inner wall of the housing, and cleansed compressed air is made to flow through the center of the housing.
The compressed air supplied through the suction pipe may be met by an obstruction plate, and with the flow thus converted to a rotational state, the compressed air may rotate along the circumferential direction around the vent within a preliminary swirl chamber formed inside the housing, thereby undergoing preliminary centrifugation based on the density difference between gases and liquids.
The compressed air that has passed through the preliminary swirl chamber may maintain a helical flow in a second swirl chamber, which is formed between the inner surface of the housing and the exhaust drum, along the multiple rows of spiral grooves formed in the circumference of the exhaust drum, so that the centrifugal force may apply gas-liquid separation based on density difference. The liquid centrifuged from the compressed air may move through the gap between the inner wall of the housing and the perimeter of the multiple rows of spiral grooves and may adhere to the inner wall of the housing to be later removed.
With the helical flow maintained in the second swirl chamber formed between the inner surface of the housing and the exhaust drum, a strong centrifugal force may be applied for gas-liquid separation based on density difference, with the liquid having a higher density separated from the gas having a lower density. Thus, the purified gas may pass through a vent formed in the lower portion of the exhaust drum and maintain helical flow in a third swirl chamber, so that any remaining liquid component may once more be centrifuged, and may pass along the rotational axis to the exhaust pipe, while the remaining condensate may be discharged at the lower part of the exhaust drum, for increased dehumidifying efficiency.
The gas purified by centrifugation may pass through a vent and through an outlet nipple connected to the exhaust pipe and external gas piping, to be sent to a pneumatic device. The liquid or condensate separated in the second swirl chamber and third swirl chamber may gather in a discharge bath within a discharge drum located at a lower portion of the housing, and may pass through a final discharge opening and through a trap to be discharged to the exterior.
However, as the compressed air moves from the first swirl chamber to the second swirl chamber and third swirl chamber, the flow merely maintains a helical form, and the centrifugal force becomes increasingly weaker. Thus, the separation of moisture and foreign substances from the compressed air may be decreased in efficiency, and it may be difficult to separate minute foreign substances.